Dru has asked for the wisdom of the Perl Monks concerning the following question:

Hello Monks,

I have been needing your help a lot lately. This is a followup question to Is Using Threads Slower Than Not Using Threads?. I am trying to optimize my code to deal with a large list of ip addresses against a large text file.

Could you please school me on how to access the keys of a hash reference without using a for loop? I thought exists $ipsAll->{key}) was the way, but that appears to be how to access the values of the keys. 
use warnings;
use strict;
use Regexp::Common qw /net/;

my $fw_file = 'tmp.log';

my @allIps = qw(10.8.1.5 10.8.1.6 10.8.1.7);
my %ipsMatch = map {$_ => 1} @allIps;
my @infectedIps = check_fw_logs(\%ipsMatch, $fw_file);

sub check_fw_logs { 

 # Sample Line to match
 Oct 31 23:58:12 x.x.x.x Oct 31 2010 23:58:14: 
<br>%PIX-5-106100: access-list INBOUND denied udp 
<br>outside/10.158.53.2(12143) -> dmz/192.168.19.11(53)
<br> hit-cnt 8 300-second interval [0x6be0682a, 0x0]
 
 my $ipsAll, $file = @_;
 my (@infectedIps);

 open (FILE, $file) or croak("Can't open $file: $!\n");
 while(<FILE>){
  my $sub = substr($_, 105, 40);
  if ($sub =~ /(\d+\.\d+\.\d+\.\d+)\(?:\d+\) -> 
outside\/(\d+\.\d+\.\d+\.\d+)/ && exists $ipsAll->{$1}){
    push(@infectedIps,$1);
  }
 }
 return @infectedIps;
}

[download]

Thanks,
Dru

Perl, the Leatherman of Programming languages. - qazwart

Replies are listed 'Best First'.
Re: Access the Keys of a Hash Reference Without a For Loop
by umasuresh (Hermit) on Nov 01, 2010 at 17:47 UTC
    I am not sure if this is what you are looking for: 
    my @keys = keys %{$hash_ref};

    [download]
[reply]
[d/l]
Re: Access the Keys of a Hash Reference Without a For Loop
by wink (Scribe) on Nov 01, 2010 at 18:28 UTC
    exists $ipsAll->{$key} will return 1 (true) if the key exists. If you need to get a list of the keys, umasuresh's answer is what you want. Also, be careful about using exists on nested hash references, since the -> operator will create intervening values. 
    my %hash = ('foo' => 'foo');
my $ref = \%hash;
print exists $ref->{'foo'};          #Prints 1 (true)
print exists $ref->{'bar'}->{'baz'}; #Prints nothing (false)
print exists $ref->{'bar'};          #Prints 1 (true)

    [download]
[reply]
[d/l]
      Thanks wink, I was just about to post to say I realized my code was actually correct and it will print out 1 (meaning it's true) if there was a match, basically what you said.

      Thanks,
      Dru

      Perl, the Leatherman of Programming languages. - qazwart
[reply]
[d/l]
Re: Access the Keys of a Hash Reference Without a For Loop
by Jim (Curate) on Nov 01, 2010 at 17:58 UTC 
    #!perl

use strict;
use warnings;

my $state_capital_of;

$state_capital_of->{'Alabama'}    = 'Montgomery';
$state_capital_of->{'Alaska'}     = 'Juneau';
$state_capital_of->{'Arizona'}    = 'Phoenix';
$state_capital_of->{'Arkansas'}   = 'Little Rock';
$state_capital_of->{'California'} = 'Sacramento';

print "$state_capital_of->{'Alabama'}\n";
print "$state_capital_of->{'Alaska'}\n";
print "$state_capital_of->{'Arizona'}\n";
print "$state_capital_of->{'Arkansas'}\n";

my $state = 'California';

print "$state_capital_of->{$state}\n"
    if exists $state_capital_of->{$state};

    [download]

    This prints

    Montgomery
Juneau
Phoenix
Little Rock
Sacramento

[reply]
[d/l]

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